Oki OKIFAX 5400 Maintenance Manual page 202

Test other fax machine under the same
conditions, especially concerning step
1-4.
Do they receive normally?
The hardware of the troubled fax
machine may be damaged.
Go to 7.13 (High-speed Modem Test)
to localize the cause.
40838301TH Rev.1
A
No
Yes
7 - 12
Check the line and the network.
Note : Even if the high-speed modem test
results in success, 300 bps signal route
remains unchecked. In that case, the
most suspected unit is MCNT board.